When you downloaded the ZIP file package, unzip it into a temporary location. You will notice there is an .inf file among them.

For 32-bit Windows, you should be able to just right-click this .inf file and choose Install.

For 64-bit Windows, the process is slightly more complicated and an instruction sheet is contained within the zip file. Note here it is important that the cmd prompt must be Run As Administrator for this process to work. A good way to do this is to search for cmd.exe on the Start Menu, then right click the result and choose Run As Administrator before proceeding with the rest of the instructions.

If you are having trouble and need help, post a comment in the Songtrix forum, or search to see if someone else has also had the same problem.